1. Field of the Invention
The present invention concerns a coupling, including:
a housing with a cutout at the first end;
a cylindric shaft extending transversely to the cutout through aligned openings at each side of the cutout;
a hook having a width which is less than the width of the cutout and which has a receiving opening with a diameter corresponding to the shaft diameter, and which is intended for receiving the shaft and an insertion opening having a width which is less than the shaft diameter and which is oriented at an angle relative to a direction of pull by loading the hook, where the shaft at a part for disposition in the cutout is provided with opposing flats with a width at least corresponding to the width of the hook and with mutual spacing which is less than the width of the insertion opening.
Furthermore, the invention concerns the use of such a coupling.
2. Description of Related Art
Hoisting systems for internally moving persons is an important part of the equipment in, e.g., a hospital or a nursing home. These enable moving entirely or partially immobile patients or inhabitants between their bed, toilet, bath or other place of stay, without the care assistants having to do heavy lifting.
Hoisting systems of this type often consist of an overhead rail system with a trolley that enables horizontal displacement, and a hoisting system suspended from the trolley that enables vertical displacement. An apron is put on the person, and the apron is connected to the hoisting system, typically via lifting bracket.
The hoisting system is provided with one or more motors for performing the vertical movement. Moreover, the trolley can be connected with one or more motors performing the horizontal movement. Alternatively, horizontal movement can be effected manually by a care assistant pushing the hoisting system or the person to be moved.
The hoist system may alternatively, instead of being ceiling-mounted, be mounted on a mobile unit with wheels under it. The patient may hereby be moved independently of a fixed overhead rail system.
Operation of the various functions is performed by the care assistant or the person himself via a control on the hoisting system or a handheld control unit.
Examples of such hoisting systems are known from U.S. Pat. No. 7,237,491 B2 or U.S. Pat. No. 6,523,195 B1.
By all these systems it is important that the strap is fastened to the lifting bracket in a safe way such that one avoids loosing the person to be lifted. This is effected by a coupling which is disposed between the strap and the lifting bracket.
It is a requirement that the coupling contains means that prevent the lifting bracket from being released when the hoist system is in use and loaded. The means are to be fail-safe such that they preclude deliberate as well as inadvertent release when the hoist system is loaded.
There exist prior art couplings where the hook grips around a shaft, where the shaft is provided with flats that may pass the insertion opening of the hook when the insertion opening has a correct angle relative to the shaft. This angle is different from the angle of a hook in relation to a shaft in use. When the hook is turned to the angle during use, it is no longer possible for the flats to pass the insertion opening. This makes it difficult to release the hook when it is loaded. The drawback of the prior art system is that there is a risk that the hook is released when the system has been completely unloaded and then lifting is performed afterwards. In this situation, the hook may come partly out of engagement with the shaft if the hook during unloading is turned to an angle where the flats may pass the insertion opening.